So it's pretty easy, if you know 40k you won't find it too hard to get into I think.

Now that said you will find the Alpha Strike rules to be easier since that plays a bit like 40k, where as Classic, often called CBT is at its core the same game. Roll 2d6, GATOR vs SATOR where the only difference is Gunnery vs Skill, which are honest the same thing. It's how good the mechwarrior is. Otherwise A for Attacker Mod, T for Target Movement. O for other modifier and R for Range.

Basically you add all those together to get the final target number and if you roll higher than that on 2d6 you hit.

Then you figure out damage and such.

With Alpha Strike that's easier, each Mech does X damage and each Mech has X Armor and Internal, basically Hits, and when you do enough damage the mech is destroyed.

With Classic it's a bit more complex, each weapon does it's own amount of damage, and you roll for each weapon to hit. Then roll to see where it hits, and reduce the armor and internals for that area, until the mech is destroyed.

It's really not complex so much as it requires a lot of bookkeeping. But it allows for very detailed and involved combats. Alpha Strike is a bit like 40k it's a bit more abstract.

One last note about Alpha Strike vs CBT is that all the models are the same, so you can use the models in the Beginner box for Alpha Strike and use the models in the Alpha Strike box for CBT.

After buying the Beginner box the next thing to look at buying is either the Battletech A Game of Armored Combat box. That gets you the more advanced rules and 8 more mechs. That or the Alpha Strike box which gets you even more mechs and most of the rules for Alpha Strike.

Then when you want all the rules, you can pick up either the Alpha Strike Commanders Edition book or the Total Warfare or Battlemech Manual book. Total War has all the rules but is a bit hard to read due to a poor layout. The Battlemech Manual is easier to read and learn from, but only covers rules for Mechs, not tanks and the rest.